In superjunction devices, oppositely doped semiconductor regions formed in a drift layer effectively cancel out their mobile charge and the resulting depleted region supports high voltage during off-state even at comparatively high dopant concentrations the semiconductor regions. On the other hand the high doping of the doped semiconductor regions ensures low on-state resistance. Typically, manufacture of superjunction devices includes growing n-type epitaxy layers and implanting p-type impurities in each epitaxy layer before forming the next n-type epitaxy layer. A less elaborate approach includes etching trenches in an n-doped epitaxial layer and filling the trenches with p-type semiconductor material. Since with the conventional trench approach further parameters such as trench width and trench taper influence a degree of compensation between the p-type and n-type semiconductor regions, device parameters of superjunction devices based on the trench approach typically show significant fluctuations. Forming the n-type and p-type semiconductor regions from thin p-doped and n-doped layers deposited along sidewalls of trenches results in significant interdiffusion between the dopants. In the interdiffused regions charge carrier mobility is reduced and therefore the on-state resistance comparatively high.
It is desirable to reduce manufacturing costs of superjunction devices without adverse impact on the device parameters.